This invention relates to a system for generating signals for the control or regulation of an automotive undercarriage.
Essential for the design of an automotive undercarriage is an efficient suspension and/or damping system. To be taken into account here, for one, is road safety while for another it is desirable to afford the passengers and a shock-sensitive cargo of the vehicle a maximally high travel comfort. From the vantage point of the suspension and/or damping system, these are contradictory objectives. High travel comfort is achieved through a maximally soft undercarriage adjustment, whereas with regard to road safety a maximally hard undercarriage adjustment is desirable.
To resolve this conflict in objectives, a switch is made from the passive undercarriages as largely used in the prior art to controlled (active) undercarriages. Depending on the predicted use of the vehicle, a passive undercarriage is designed either relatively hard ("sporty") or relatively soft ("comfortable") when installed. The characteristic of the undercarriage during the operation of the vehicle can not be influenced with these systems. In the case of active undercarriages, in contrast, the characteristic of the spring and/or damping system can be influenced during road operation, depending on driving conditions.
In the German patent disclosure 38 27 737 the aforementioned conflict in objectives between road safety and driving comfort is solved in that an active or switchable undercarriage is at varying operating conditions, for instance changing road surface conditions, so controlled under variation of the travel comfort that the road safety is always assured. Utilized as an evaluation criterion for the road safety is the effective value of the wheel load fluctuations during road operation. Wheel load fluctuation is understood as the variation of the wheel load (normal force between tire and road surface) from its static value. The wheel load fluctuation (as also the wheel load itself), however, is accessible to direct measurement only with great difficulty, since sensors would need to be arranged between the wheel or the tire and the road surface. In contrast, the measurement of the spring travel is relatively simple and cost-effective to realize. Termed spring travel is the relative displacement of the vehicle body relative to the wheel. According to DE-OS 38 27 737, the spring travel is measured as a substitute variable for the wheel load fluctuation. Derived from these measured values are the sliding effective value and the sliding average for the substitute variable as well as their difference. Once this difference has been compared with a predetermined set value, exceeding this set value causes the issuance of an electrical display and/or control signal for control/regulation of the undercarriage.
The problem underlying the present inventional system, basing on signals which represent the relative movements between vehicle body and the wheels, is to generate on the basis of more differentiated evaluation criteria control signals for an adjustable undercarriage in order to, as the case may be, effectively increase the road safety.